Question 1

What is eGFR and why does it matter?

Accepted Answer

Glomerular filtration rate (GFR) measures how well the kidneys filter waste from the blood, and is considered the best overall indicator of kidney function. Because directly measuring GFR is impractical in routine care, clinicians estimate it (eGFR) from a blood test for serum creatinine, along with age and sex.

Question 2

What formula does this calculator use?

Accepted Answer

This tool uses the 2021 CKD-EPI creatinine equation, which removed race as a variable following a 2021 joint task force review by major U.S. kidney health organizations. It is the equation most commonly recommended for adult eGFR reporting today.

Question 3

Is a low eGFR always a sign of kidney disease?

Accepted Answer

Not on its own. Chronic kidney disease is generally defined by reduced eGFR or other markers of kidney damage persisting for three months or longer, so a single low reading can also reflect dehydration, recent illness, certain medications, or lab variation. Trends over repeated tests, along with a urine albumin test, give a clearer picture.

Question 4

Why is this only for adults?

Accepted Answer

The CKD-EPI 2021 equation used here was derived and validated in adult populations. Children and adolescents need age- and height-based pediatric equations instead, which estimate kidney function differently as the body is still growing.

Question 5

Can I use this if I only have a cystatin C result, not creatinine?

Accepted Answer

This particular tool is creatinine-based. Some labs also report a creatinine-cystatin C combined equation, which can be more accurate in certain situations — ask your healthcare provider which result is most relevant to your care.

Stage	eGFR range	Description
G1	≥ 90	Normal or high
G2	60–89	Mildly decreased
G3a	45–59	Mildly to moderately decreased
G3b	30–44	Moderately to severely decreased
G4	15–29	Severely decreased
G5	< 15	Kidney failure

eGFR Calculator

How eGFR is calculated

CKD stages by eGFR

Common questions